Sidebar mode gives feedback more room to write
Sidebar mode opens the feedback form as a panel sliding in from the side of the page instead of a small floating modal. The point is space. Users writing more than a line of feedback were running out of room in the floating widget.

The floating widget is unchanged and still supported. Sidebar mode is a configuration option, not a replacement.
Set the modal position when you build your snippet, or in your framework plugin's configuration.
On documentation sites, a right-hand sidebar is the less disruptive choice. The reader keeps the page in view while writing about it.
Visual feedback covers the rest of the modal, and the installation reference has the option names per framework.